A computational fluid dynamics model of a rotary regenerative heat exchanger in a flue gas desulfurization system

Abstract

Rotary regenerative heat exchangers (RHEX) are commonly used in flue gas desulfurization (FGD) systems to improve the dispersion of pollutants, reduce the visible plume, avoid liquid droplet rainout from the stack and avoid corrosion problems on the system materials. In this study, transient behaviors of heating and cooling cycles of a rotary regenerative heat exchanger in an FGD system were investigated via a 3-D computational fluid dynamics (CFD) model. For this purpose, the rotary regenerative heat exchanger was modelled using porous media approach for the heat transfer surfaces (i.e. matrix) inside the heat exchanger. A standalone channel model as used to obtain porous media parameters and heat transfer coefficient. Numerical results confirmed by published literature. Effects of different operating conditions on the performance of the heat exchanger have been investigated. In conclusion treated gas outlet temperature increases with increasing angular velocity and treated gas inlet temperature while it decreases with decreasing load. Consequently, untreated gas outlet temperature decreases with increasing angular velocity and decreases with the decreasing treated gas inlet temperature and load. By means of overall system performance it is observed that overall system performance increases with decreasing angular velocity and treated gas inlet temperature while it increases with decreasing load.